The Path-Way to Knowledg, Containing the First Principles of GeometrieRecord, Robert
Science
The Path-Way to Knowledg, Containing the First Principles of Geometrie
Record, Robert
Geometry -- Early works to 1800
First for example of a sharpe ãgle let A. stãd & B.C shal be y^e
lyne assigned. Thẽ do I make a triangle, by adding B.C, as a
thirde side to those other ij. which doo include the ãgle
assigned, and that triãgle is D.E.F, so y^t E.F. is the line
appointed, and D. is the angle assigned. Then doo I drawe a
portion of a circle about that triangle, from the one ende of
that line assigned vnto the other, that is to saie, from E.
a long by D. vnto F, whiche portion is euermore greatter then
the halfe of the circle, by reason that the angle is a sharpe
angle. But if the angle be right (as in the second exaumple you
see it) then shall the portion of the circle that containeth
that angle, euer more be the iuste halfe of a circle. And when
the angle is a blunte angle, as the thirde exaumple dooeth
propounde, then shall the portion of the circle euermore be
lesse then the halfe circle. So in the seconde example, G. is
the right angle assigned, and H.K. is the lyne appointed, and
L.M.N. the portion of the circle aunsweryng thereto. In the
third exaumple, O. is the blunte corner assigned, P.Q. is the
line, and R.S.T. is the portion of the circle, that containeth
that blũt corner, and is drawen on R.T. the line appointed.
THE XXXII. CONCLVSION.
To cutte of from a circle appointed, a portion containyng an
angle equall to a right lyned angle assigned.
When the angle and the circle are assigned, first draw a touch
line vnto that circle, and then drawe an other line from the
pricke of the touchyng to one side of the circle, so that
thereby those two lynes do make an angle equall to the angle
assigned. Then saie I that the portion of the circle of the
contrarie side to the angle drawen, is the parte that you seke
for.
_Example._
[Illustration]
A. is the angle appointed, and D.E.F. is the circle assigned,
frõ which I must cut away a portiõ that doth contain an angle
equall to this angle A. Therfore first I do draw a touche line
to the circle assigned, and that touch line is B.C, the very
pricke of the touche is D, from whiche D. I drawe a lyne D.E, so
that the angle made of those two lines be equall to the angle
appointed. Then say I, that the arch of the circle D.F.E, is the
arche that I seke after. For if I doo deuide that arche in the
middle (as here is done in F.) and so draw thence two lines, one
to D, and the other to E, then will the angle F, be equall to
the angle assigned.
THE XXXIII. CONCLVSION.
To make a square quadrate in a circle assigned.
Draw .ij. diameters in the circle, so that they runne a crosse,
and that they make .iiij. right angles. Then drawe .iiij. lines,
that may ioyne the .iiij. ends of those diameters, one to an
other, and then haue you made a square quadrate in the circle
appointed.
_Example._
[Illustration]
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